ABSTRACT
Objective:To establish a candidate reference method for the determination of angiotensin Ⅱ in human plasma by isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) and to evaluate its performance.Methods:Using [ 13C 6- 15N]-angiotensin Ⅱ as the internal standard, the plasma was accurately weighed by gravimetric method and mixed with a certain amount of internal standard. At the same time, enzyme inhibitor was added. After zinc sulfate solution protein precipitation and reversed-phase solid-phase extraction plate treatment, it was analyzed by liquid chromatography tandem mass spectrometry. The multi reaction ion monitoring mode(MRM)was selected by mass spectrometry to detect specific ion fragments of angiotensin Ⅱ and internal standard. The linearity, sensitivity, precision, recovery rate and uncertainty of the performance of the established method were evaluated according to ISO15193. Results:Angiotensin Ⅱ had good linearity in the range of 10-1 000 pg/g ( r=0.999 5), the lower limit of quantification was 7.68 pg/g, the analytical recoveries were 97.14% to 102.85%, intra-batch imprecision≤3.21%, inter-batch imprecision≤2.96%, and total imprecision≤3.67%. Conclusion:A method for the determination of plasma angiotensin Ⅱ was established by ID-LC-MS/MS. The method is accurate and reliable, and is expected to be a reference method for the determination of plasma angiotensin Ⅱ.
ABSTRACT
Objective To develop a candidate reference method for the determination of serum creatinine and to evaluate the ac-curacy of conventional detection systems though method comparison to achieve traceability .Methods The candidate reference method was established according to the sarcosine oxidase and the accuracy and reliability of the method was verified through par-ticipation in international reference laboratories EQA activities (IFCC-RELA) .20 fresh single human serum samples with different concentration and calibrator were simultaneously measured by using conventional detection system and candidate reference method . Results The calibration curve for serum creatinine was linear in the concentration range from 50-2 000 μmol/L with a correlation coefficient of 0 .999 9 under the optimum experimental conditions (the linear equation was Y=0 .000 884 2X-0 .000 325 3) and the imprecision was less than 1 .0% .The proposed method has been applied to the determination of RELA samples with satisfactory re-sults .The measured results with conventional detection systems were consistent with candidate reference method ,and the slope of the regression equation was 1 .005 6 .Conclusion The candidate reference method of serum creatinine is successfully established and which can be used for traceability and standardization .It may provide an effective way for conventional detection system traceable to the reference method or reference material .
ABSTRACT
Objective To establish a candidate reference method for the determination of serum lithium based on ion chromatog-raphy and evaluate its analytical performance.Methods A simple sample treatment procedure,which can be remove the proteins and/or organics in human serum,has been developed for the determination of serum lithium.Method precision was evaluated with different concentration of fresh human serum and EQA sample RELA-A/B.Method accuracy was investigated with the recovery ex-periments in fresh human serum and RELA-A/B sample.Results The linear equation was Y =0.817 1X -0.001 3 with a correla-tion coefficient of 0.999 95 under the optimum experimental conditions,the detection limit (3S/N)for lithium was 6 μg/L and the imprecision was less than 1.0%.The results of the recovery experiments indicated that the recoveries were reasonable for the deter-mination of serum lithium,in a range of 99%-101%.Conclusion The candidate reference method of lithium was successfully es-tablished and which can be used for traceability and standardization.It may provide an effective way for routine testing of lithium traceable to the reference method/reference material.